1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the semiconductor device, and more particularly to the passivation of the periphery of a bump to be formed on an electrode pad.
2. Description of the Related Art
When a semiconductor device such as a VLSI (very large scale integration) is to be manufactured, a passivation structure is very important around a bump formed on an electrode pad, and various endeavors have been made to enhance a productivity while maintaining a reliability.
In recent years, a structure using a polyimide resin for a passivation film has variously been proposed. By way of example, as shown in FIG. 15, there are formed an electrode pad 2 comprising an aluminum layer formed to come in contact with a surface of a semiconductor substrate 1 or a wiring layer provided on the surface of the semiconductor substrate, and a metal bump 6 formed in a contact hole H provided on a silicon nitride film 3 for covering the upper layer of the electrode pad 2 through a TiW layer to be an intermediate layer 4. The metal bump is formed on a thin metal layer formed by sputtering to be a seed layer 5 during plating, and a polyimide resin film 7 to be a passivation film is formed around the metal bump 6.
Such a structure is formed through the following manufacturing process.
First of all, a wiring layer (not shown) and an interlayer insulating film (not shown) are formed on the surface of the silicon substrate 1 provided with an element region and a through hole (not shown) is formed by photolithography. Then, the aluminum layer is evaporated and the wiring (not shown) and the electrode pad 2 are subjected to patterning by the photolithography. Thereafter, the silicon nitride film 3 is formed on the upper layer of the wiring and the electrode pad 2 and is subjected to patterning by the photolithography, and a contact hole H is formed in the central part of the electrode pad 2 to cover the peripheral edge of the electrode pad 2 with a silicon nitride film (FIG. 16).
As shown in FIG. 17, subsequently, the polyimide resin film 7 to be a passivation film is formed and is subjected to patterning, thereby exposing the electrode pad 2 as shown in FIG. 18.
If the aluminum layer is exposed to a surface, it is apt to be corroded. As shown in FIG. 19, therefore, a titanium tungsten TiW film to be a barrier layer is formed as the intermediate layer 4 on the aluminum layer by the sputtering method and the metal layer 5 to be a bonding pad is then formed.
As shown in FIG. 20, thereafter, the metal layer 5 and the intermediate layer 4 are subjected to patterning by the photolithography.
Accordingly, it is desirable that the edge of the pad layer 5 is coincident with that of the polyimide resin film 7. In consideration of mask precision, there is a problem in that the edges are coincident with difficulty. On the other hand, there is a problem in that a short circuit is apt to be caused if the metal layer 5 and the intermediate layer 4 get over the passivation film 7. For this reason, the patterning is carried out in consideration of precision in the photolithography.
As shown in FIG. 21, furthermore, the plated layer 6 is formed on the metal layer 5 by electroplating, thereby forming a bump.
As described above, in the method, a clearance is generated between the polyimide resin film constituting the passivation film and the metal layer 6 constituting the bump, and the TiW surface which is oxidized easily is exposed. For this reason, there is a problem in that corrosion is apt to be caused, the passivation effect cannot be obtained well and the reliability is thereby deteriorated.
In the conventional pad structure, thus, there is a problem in that a water content enters from the clearance between the passivation film and the bump, the electrode pad such as aluminum is easily corroded and the reliability is thereby maintained with difficulty.